1. Field of the Invention
The present invention relates generally to semiconductor processing. In particular, the present invention relates to a system that provides rapid cooling of the heater block structure located within the processing chamber of a wafer processing apparatus.
2. Description of the Related Art
In the semiconductor industry, wafers are commonly processed using a gas process known as chemical vapor deposition (xe2x80x9cCVDxe2x80x9d). The CVD process forms thin layers of material over an integrated circuit substrate using thermal and/or plasma decomposition and reaction of selected gases. Conventional CVD materials include silicon dioxide, silicon nitride, and polysilicon, as well as a wide variety of well known CVD materials suitable for insulators and dielectrics, semiconductors, conductors, superconductors, and magnetics.
The processing chamber 10 of a conventional CVD processing apparatus is shown in FIGS. 1 and 2. The processing chamber 10 communicates with a load chamber 11 from which wafers to be processed are introduced into the processing chamber 10, and into which processed wafers are received from the processing chamber 10. Chamber gases are exhausted through vent ports. A system for moving waters from station to station in the processing chamber 10 includes a wafer transport mechanism 13.
FIG. 1 is a top view of the load chamber 11 and processing chamber 10 with the top plate 14 removed from the processing chamber 10. FIG. 2 is a side view of the processing chamber 10 with the top plate 14 in place and ready for high pressure CVD processing. A plurality of process stations 15 are provided at circumferentially spaced locations within the processing chamber 10. Each process station 15 includes, for example, a dispersion head 16 for introducing a process gas or gas mixture over a wafer to be processed, in coordination with activation of the wafer transport mechanism 13. A vacuum exhaust port 17, and a wafer transfer mechanism 18, are also provided, each of which is well known in the art.
In order to stimulate the deposition of material onto the wafer being processed, heat must be provided to the wafer. One method of providing heat to the wafer involves heating a heater block 20 having a large mass, which transfers heat to the wafers sitting respectively thereon. A resistive heating element or other suitable heating mechanism provides the necessary heat to the heater block 20. The heater block 20 typically has a temperature during wafer processing of approximately 300 to 400xc2x0 C.
During both routine and unplanned maintenance and repair operations of the wafer processing apparatus, the heater block 20 must be cooled from its normal operating temperature down to a safe working temperature of approximately 50xc2x0 C. The conventional method of heater block cooling during such maintenance operations is to turn off the heater breaker at the start of the gas line flush step. The cooling begins at that time under vacuum. After completion of several full gas line flushes, a 30 minute atmospheric chamber purge is performed to remove residual HF from the chamber. Approximately one hour elapses during these operations, during which time the heater block 20 cools from its initial 400xc2x0 C. down to about 305xc2x0 C. under vacuum. At that time, the chamber 10 is opened and allowed to cool to a safe working temperature by free convection. The total time for cooling from 400xc2x0 C. to 50xc2x0 C. is about 4 hours 20 minutes (260 minutes). Since routine maintenance operations typically occur monthly, and other unplanned maintenance and repairs are necessary at irregular intervals, the heater block cooling time described above results in a large amount of down time for the wafer processing apparatus.
A heater block cooling system has been developed recently by Novellus Systems, Inc. to minimize the down time required for cooling the heater block. This heater block cooling system includes a HEPA-filtered high flow vacuum system connected by a flexible duct to an aluminum shroud. The shroud is a two-piece design (two halves) connected by xc2xc turn fasteners. A gasketed lip is provided near the lower edge of the shroud halves. The lip of each shroud half is placed on the chamber barrel, and the two halves of the shroud are jointed by six xc2xc turn fasteners. The chamber top plate is then lowered onto the gasketed upper lip of the shroud to hold the shroud securely. The high-flow HEPA vacuum is then turned on. Cool fab air (70xc2x0 F.) flows into the shroud through the five ports in the shroud. Baffles help to direct the air flow over the heater block surface, and the air exits through the nozzle/flex duct on the opposite side of the shroud. The heated air is then HEPA-filtered and exhausted back into the fab. This heater block cooling system decreases the time required for cooling the heater block. However, this cooling system is relatively complex, bulky and difficult to assemble to the chamber during maintenance operations.
Thus, there is a need for an improved heater block cooling system that can be used with processing chambers 10 of existing wafer processing machines to facilitate maintenance operations and reduce the down time required for cooling the heater block 20.
It is an object of the present invention to provide an apparatus for cooling the heater block in a processing chamber of a wafer processing machine that solves the problems with the prior art arrangements described above.
It is a further object of the present invention to provide a heater block cooling system and method that minimize the down time required for maintenance operations of a wafer processing machine by cooling the heater block rapidly using forced air circulation.
It is a still further object of the present invention to provide a heater block cooling system that is simple to manufacture, fast and easy to install, reliable and efficient in use, and readily adapted to fit processing chambers having different diameters and configurations.
According to the present invention, a heater block cooling system and method are provided for cooling a heater block located in a cylindrical processing chamber of a wafer processing apparatus. The cooling system includes first and second frame assemblies having respective ends adapted to rest on an upper peripheral surface of the processing chamber, and a plurality of fan assemblies mounted to the frame assemblies at spaced locations therealong. A first pair of fan assemblies are directed to push air into the processing chamber, and a second pair of fan assemblies are directed to pull air out of the processing chamber. The fan assemblies are arranged such that they circulate ambient air through the processing chamber to provide a rapid cooling of the heater block to a safe working temperature. The frame assemblies have an adjustable length that can be adjusted to fit processing chambers having different sizes and configurations. The cooling system according to the present invention substantially reduces the cooling time required for the heater block to reach a safe working temperature, as compared to conventional cooling by free convection.
According to a broad aspect of the present invention, a cooling system is provided for cooling a heater block in a processing chamber of a wafer processing apparatus, comprising: first and second frame assemblies having respective ends adapted to rest on an upper peripheral surface of a processing chamber; and a plurality of fan assemblies mounted to the frame assemblies at spaced locations therealong for circulating ambient air through the processing chamber.
According to another broad aspect of the present invention, a method is provided for cooling a heater block contained within a processing chamber of a wafer processing apparatus, comprising the steps of: providing a processing chamber having a generally cylindrical shape, a top plate that covers the processing chamber during wafer processing, and a heater block positioned within the processing chamber; removing the top plate to expose an open upper end of the processing chamber; placing a cooling system across the open upper end of the processing chamber, the cooling system having a plurality of fan assemblies mounted to a frame at spaced locations therealong; and operating the fan assemblies to circulate ambient air through the processing chamber for a sufficient time to cool the heater block to a safe working temperature.
Numerous other objects of the present invention will be apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of the present invention, simply by way of illustration of one of the modes best suited to carry out the invention. As will be realized, the invention is capable of other different embodiments, and its several details are capable of modification in various obvious aspects without departing from the invention. Accordingly, the drawings and description should be regarded as illustrative in nature and not restrictive.